Method of forming stencil sheets



Patented Dec. 30, 1941 .UNITED STATES PATENT OFFICE No Drawing.Application March 23, 1940, Serial No. 325,578

9 Claims.

The object of my invention is to provide a decalcomania for producingfacsimiles of labels on bottles, which decalcomania will be relativelyinexpensive to manufacture and apply.

A further object of my invention is to provide a decalcomania which maybe inexpensively formed in a plurality of colors, each color of whichwill exactly register with the other colors. Heretofore, the manufactureof multi-colored vitreous transfers has been exceedingly costly andentailed great difficulty because of the care required to secureaccurate alignment of the various colors. cially use the lithographicprocess with vitreous colors because vitreous ink is composed mainly ofpulverized colored glass which does not lend itself to application by aroller. When the screen proces of printing has been tried, it has beenpossible to use only a single color because of the almost impossibilityof producing screens for the individual colors which accurately registerwith each other. As a result, only two processes of vitreous labelingare commercially employed. The first and most preferable comprisesapplying the ink directly to the bottle through a screen. Only one colorcan be used with such a process because a separate screen must be madefor each subsequent color, which screens are more diflicult to make andregister on a bottle than they are on a flat piece of transfer paper.

The second process comprises using transfers,

but, invariably, such transfers are made in a manner different than theapplicants. These transfers have all, to the applicant's knowledge, beenmade by the powdering process wherein the transfer paper is coated withlacquer or lithographers' varnish and before the varnish dries thepowdered glass is dusted onto the sticky varnish to form the ink. Solittle glass will stick to the varnish that subsequent applications mustbe made if an opaque label is to be had. These subsequent operations arenot only expensive but tend to make the edges of the work blurry. Itwill be apparent that in labels requiring fine detail it is imperativethat each color be applied all in one operation to prevent blurring.Even when several coats of the powder have been applied by dusting solittle color is present that it is usually necessary to back up thedesigns with a separate layer of white glass.

In my improved process the color may be applied as thickly as desired,which not only forms better appearing labels but also gives sufllcientrigidity to the transfer that it may be removed It has been impossibleto commerfrom the transfer paper and deposited on the bottle withoutdanger of breakage.

Specifically, my invention relates to a new method of making screenswhereby a plurality of colors may be successively applied to thetransfer paper, and which screens will all be in accurate registry witheach other to thus prevent overlapping of the colors.

My invention further relates to the composition of the transfer coating,my improved composition producing a transfer of greater mechanicalstrength to thereby be more easily slid oi! the paper and applied to thebottle, and one which will burn to a better finish than the present typeof coating. Only the glass remains after firing so that any binder usedmust burn to a colorless ash and avoid checking of the glass. Myimproved composition is believed to produce a better label in thisrespect than other compositions now being used.

The reason that multi-colored screen work has not been successful isthat in making the screens the tissue, as the sensitized material isknown, must be exposed, then developed and then stretched over thescreen. It has been practically impossible to control the expansion andstretch of the tissue in various directions so that the screens do notaccurately register. With my improved process accurate registry isassured.

With these and other objects in view, my invention consists in thedecalcomania, per se, and the steps comprisingmy improved process, asclaimed in my claims and described in my specification.

To carry out my improved process a positive photographic glass plate ismade for each color of the label, the plates being made in theconventional manner. Each plate has an area thereon corresponding to oneof the colors desired. The glass plates should be of uniform size andthe designs located thereon so that final registry of the colors iseasily obtained.

After these plates are dried a coating of rubber solution is flowed overthe emulsion side of each plate. This rubber solution consists of acolorless latex which rapidly dries to a very thin film which is hardlydiscernible to the eye but which is insoluble in water. The waterinsoluble film is very important in this method.

on one side. After being treated in the bichromate solution the tissue,while still wet, is placed against the waxed surface of the plate, justdescribed, with the waxed surface against the gelatin side of thetissue. The tissue, while still wet, is exposed through the plate and isthen washed in water at 120 F., at which time the paper is peeled offfrom the gelatin leaving the gelatin coating adhering to the waxedsurface. The soluble portions of the gelatin are now washed away leavinga relatively thick negative film adhering to the positive plate. Theplate is now placed in cold water at 55 to 65 F. It may be well tomention that the concentration of bichromate and the exposure time canbe regulated to produce in an insoluble film of any reasonable thicknessand one which is much thicker than the maximum desirable thickness ofpaint required on the transfer. The thickness of this gelatin film isquite important as it controls the thickness of paint on thedecalcomania.

While the aforementioned plate is still wet a fine mesh screen is placedover the gelatin side and pressed uniformly against the gelatin. Thescreen may be either a fine mesh silk screen as is commonly used in thescreen printing process or it may be a wire mesh screen which stands upbetter with ceramic paint. A screen of 200 threads per inch has provedvery satisfactory. The gelatin and screen is now allowed to dry and thescreen is pulled away from the positive plate. The bichromate andgelatin adhere to the screen. It will be noted that from the time ofexposure until after the screen has dried, the tissue never leaves theglass plate so that it is held in an exact uniform position at alltimes. The dried screen is thus an exact negative of the photographicpositive.

A screen is made for each of the colors to [be applied and inasmuch aseach of the positive plates is inexact register with each other, itfollows that each of the screens must be in exact register.

In making the decalcomania, transfer paper is placed ma conventionalscreen printing machine and the first screen is brought down against thepaper with the gelatin side of the screen against the paper. The propercolor of ceramic paint is I then squeegeed through the screen onto thepaper. The colored paint which forms the background of the label ispreferrably applied first, then the color of the next importance isapplied and finally the remaining color or colors.

After the transfers have been dried they may be handled with ease, theceramic paint adhering to the paper which prevents the destruction ofeven the smallest detail. When it is desired to place the transfer uponthe bottle, it is dipped in water for a few minutes until the decorationas a whole starts to slide across the paper. The decoration is thenslipped edgewise from the pascreen, a relatively hard durable film ofthe required thickness is formed on the transfer paper. It has beensuggested that a lacquer layer be provided upon which the pulverizedglass is dusted, but it is believed that the applicants process whereinhe mixes lacquer with the pulverized glass is unique in the art. Lesspitting of the surface results than when the lacquer is applied as alayer.

Among the many advantages arising from the use of my improveddecalcomania and method of making same, it may be well to mention thatlabels or decorations of fine detail and of many colors may be formedwith one firing upon the work, which thereby materially reduces the costover those processes requiring several firings. With my improved methodof making the screens exact register of the colors is possible informing the transfers; whereas, in the past, it was not commerciallypossible to produce a series of screens which would exactly register.

Still further, by forming the screens with various sensitivities andexposures, it is possible to regulate the depth of the bichromatefilm'in acper onto the work. The bottle with the transfer thereon isthen heated to approximately 1100 F. where all the colors of paint fuseat one time as a unit to the bottle. In order that the bottles may notcrack, they are gradually brought up to this temperature and graduallycooled in the conventional manner.

As has been mentioned, labels formed from ceramic paint, even by thedusting process, are brittle because the composition of such paint isprincipally pulverized glass. In order to prevent cracking of suchlabels, I have found that by mixing lacquer with thepulverized glass andapplying the mixture of lacquer and glass through the cordance with theamount of color desired. For example, black ink, having a very goodcovering power, is not required to be nearly as thick as one of thelighter colored inks. Because of this a considerable saving is broughtabout as only the amount of ceramic paint absolutely necessary is usedin making the transfer.

Still further, by mixing the lacquer with the pulverized glass beforeapplying it to the screen, a decalcomania having a deposit thereon ofuniform composition is maintained. Thus, when the decalcomania is beingfired, the lacquer vaporizes from the whole body of the design so thatthe design dries uniformly on each bottle without checking. Where thelacquer is applied as a base upon which the powder is dusted, thelacquer must vaporize or burn away through the paint which tends tocheck the paint. In my improved process the lacquer is uniformlydistributed through the paint so that when it dries,

the check marks are much reduced and less conspicuous than with theformer process.

Some changes may be made in the sequence of the various operationscomprising; my improved method without departing from the spirit of myinvention and it is my intention to cover by my claims such changes asmay reasonably be included within the scope thereof.

I claim as my invention:

1. The method of producing printing screens comprising, applying a waterinsoluble film upon the emulsion side of a rigid photographic plate ofthe design to be printed, then applying wetted carbon tissue over saidfilm, then exposing said tissue through said plate, then developing saidtissue, then drying said tissue while still on said plate, and thenstripping said tissue from said plate along the outer surface of saidfilm.

2. The method of producing printing screens comprising, applying a waterinsoluble film over the emulsion side of a rigid photographic plate ofthe design to be printed, then applying a wetted carbon tissue over saidfilm, then exposing said tissue through said plate, then developing saidtissue and while still wet pressing a fine mesh screen into theundissolved portions of said tissue, then drying said tissue and screenwhile still upon said plate, and then stripping said tissue and screenfrom said plate along the outer surface of said film.

3. The method of producing printing screens comprising, forming a rigidphotographic plateof the design to be printed, then applying atransparent rubber coating over the emulsion side of said plate, thenapplying wetted carbon tissue over said coating, then exposing saidtissue through said plate, then developing said tissue, then drying saidtissue upon said plate, and then stripping said tissue from said platealong the outer surface of said coating.

4. The method of producing printing screens comprising, forming a rigidpositive plate of the design to be printed, then applying a transparentrubber coating over the emulsion side of said plate, then applyingwetted, carbon tissue over said coating, then exposing said tissuethrough said plate while still wet, then developing said tissue andwhile still wet pressing a fine mesh screen into the undissolvedportions of said tissue, then drying said tissue and screen while stillupon said plate, and then stripping said tissue and screen from saidplate along the outer surface of said coating.

5. The method of producing'printing screens comprising, forming a rigidpositive plate of the design to be printed, then applying a film ofcolorless latex over the emulsion side of said plate, then applying acoating of collodion over said latex film, then waxing said collodioncoating, then applying wetted carbon tissue to said waxed surface, thenexposing and developing said tissue while still wet, then drying saidtissue upon said plate, and then stripping said tissue from said platealong the outer surface of said film.

6. The method of producing printing screens comprising, forming a rigidpositive plate of the design to be printed, then applying a film ofcolorless latex over the emulsion side of said plate, then applying acoating of collodion over said latex film, then waxing said film, thenapplying wetted carbon tissue to said waxed surface, then exposing saidtissue through said plate while still wet and developing same, thenpressing a fine mesh screen into the undissolved portions of saidtissue, then drying said tissue and screen while still upon said plate,and then stripping said tissue and screen from said plate along saidwaxed surface.

' transparent rubber coating over the emulsion 7. The method ofproducing a printing screen comprising, forming a transparent positiveplate of the design to be printed, then applying a water insolubletransparent film over the emulsion side of said plate, then applying asensitized coating upon said insoluble film, then exposing saidsensitized coating through said plate and developing same, then placinga fine mesh screen upon said developed coating while'still wet andpressing same into said coating, then allowing the screen and coating todry, and then stripping said screen from said plate along the outersurface of said insoluble film.

8. The method of producing a printing screen comprising, forming atransparent positive plate of the design to be printed, then applying aside of said plate, then applying a sensitized coating upon said rubberfilm, then exposing said sensitized coating through said plate anddeveloping same, then placing a fine mesh screen upon said developedsurface and pressing same into place, them allowing said coating andscreen to dry while on said plate, and then stripping said.

plate from said screen along the outer surface of said rubber film.

9. The method of forming a printing screen comprising, photographing apositive transparent plate of the design to be printed, then flowing atransparent rubber solution over the emulsion side of said plate, thenapplying a coating of collodion on said rubber film, then waxing theouter surface of said collodion coating, then applying, while wet, atissue sensitized in a 5% bath of hich'romate solution with the gelatinside of the tissue next to said collodion surface, then exposing saidbichromate through said plate and subsequently peeling off said tissueleaving the gelatin portion of said tissue upon said collodion surface,then washing said plate until the soluble portions of the gelatine havebeen removed, then placing a screen upon said gelatin while it is stillwet, then allowing the screen and gelatin to dry as a unit upon saidplate, and then stripping said screen from said plate along the line ofsaid waxed surface.

MARCO a'crAvoLa.

